Paula DeenDropped from Cooking Expo AdsEven Though She's Headlining

8/25/2013 12:45 AM PDT

Paula Deen is headlining a giant food expo in Houston next month, but you wouldn't know it ... because two huge ticket sellers are REFUSING to put her name or her picture in the advertising, TMZ has learned.

The event is the Metro Cooking and Entertainment Show ... and Paula was supposed to be the main attraction, but sources connected with the expo tell us, Groupon and Livingsocial are actively trying to distance themselves from anything Deen-related.

Instead, the companies are featuring much lesser known chefs on their ads -- like Terry French and Martie Duncan -- and ticket sales are taking a huge hit.

A rep for the expo tells us, "It's more difficult -- I'm not going to kid -- not having those tools [Paula and her sons] to help sell tickets, but we are fighting for Paula."

Paula has been with the expo for 8 years, and the rep says tickets sold much more quickly when the chef was featured on the advertisements ... but not this year ... and there's nothing Metro can do about it (except on its own website).

FYI, the expo will be Paula's first public appearance since she settled the racial discrimination lawsuit filed against her in Georgia.